Human speech is the primary means by which we communicate with members of our species. Central to this speech is our ability to parse speech from other sounds in the environment and recognize the individual meaningful units, such as words. Because significance of this problem, we evolved specialized perceptual and neural mechanisms for speech recognition. Similarly, many animals communicate with conspecifics using vocalizations and, as such, must have evolved comparable mechanisms for vocal signal recognition. Given the anatomical and physiological similarities between all mammalian brains, studies of the behavioral and neural mechanisms underlying vocal signal recognition are likely to provide key insights into the analogous process in the human brain. This proposal aims to examine the mechanisms underlying vocal signal recognition during a species-specific vocal behavior known as antiphonal calling. Since antiphonal calls are only produced in response to a particular call type, the behavior represents a natural (i.e. untrained) recognition system. This proposal has four aims. Specific Aim 1 is to use synthetic vocalizations to examine the perceptual relevance of particular acoustic features for vocal signal recognition. Specific Aim 2 will record neurophysiological responses of individual neurons in the auditory cortex during vocal signal recognition. Specific Aim 3 will extend these physiological recordings and examine the activity of neurons in the auditory and prefrontal cortex simultaneously during antiphonal calling. Specific Aim 4 will employ pharmacological agents to inhibit specific areas of the cortex and determine the functional relationship between those populations of neurons and vocal signal recognition. Findings from this proposal will have direct relevance to our understanding of the cortical mechanisms underlying speech recognition and can aid in developing treatments for various aphasic disorders. General Summary - Like humans, many animals communicate with each other by vocalizing. By studying how the brains of animals are able to recognize their vocalizations, we will gain important insights into how speech recognition occurs in the human brain. Results from this study are applicable to research on language disorder treatments. [unreadable] [unreadable] [unreadable]